1. Field of the Invention
The invention relates to digital watermarking and watermark information and end-user access information. More particularly, the invention relates to embedding watermarking information or end-user access information into multimedia content.
2. Description of the Related Art
Watermarks are used generally to identify the origin and/or ownership of an image or other underlying content. For example, conventional watermarks can include information that identifies the owner or author of the content and/or unique product information related to the content purchase. When used with multimedia content and other digital media, such as digital video or image content, watermarks include watermark information that can be embedded into the multimedia content in a manner that makes the watermark effectively invisible or nondiscernable to the end user of the digital media, e.g., as the underlying multimedia content into which the watermark was embedded is played on, displayed on or otherwise processed or consumed by the end user device. Also, when used with multimedia content and other digital media, watermarks typically are embedded into the multimedia content in such a way that the removal or attempted removal of the watermark may destroy or visibly alter the underlying multimedia content. Alternatively, the watermark can be visible to end users and removable by authorized end users or end user devices having access to an appropriate decoder, while not being removable by unauthorized end users or end user devices. Watermarking in multimedia content and other digital media also can identify tampering, since manipulation of watermark data often can result in an invalid watermark.
End-user access information generally is any suitable information that allows (or denies) end users and/or end user devices to access and/or control associated multimedia content. For example, end-user access information can include, but is not limited to, digital rights management (DRM) information, such as security and/or control keys and/or messages, encryption and/or decryption keys, digital signature and certificate information, end user authentication information, and/or any other DRM information that allows (or denies) end user access to multimedia content, including access information in accordance with one or more DRM standards, such as the Open Mobile Alliance (OMA) standard and one or more of the Digital Video Broadcasting (DVB) standards, including DVB-H for handheld or mobile end user devices. End users access information also can include, but is not limited to, conditional access (CA) information (CAI), such as one or more scrambler, descrambler and/or control keys and/or messages, encryption and decryption control keys and/or words, entitlement control and/or entitlement management information, and/or any other access information used within a conditional access system to protect content and/or allow access to and/or control of protected content by one or more end users, including access information in accordance with one or more conditional access system standards, such as Digital Video Broadcasting-Conditional Access (DVB-CA).
Multimedia content often is coded and transmitted using a block-based video compression encoder, such as an MPEG (Moving Pictures Experts Group) encoder, which formats the stream of multimedia content according to a suitable standard, such as the MPEG-2 or MPEG-4 standard, or other suitable standard. Using block-based encoding, each frame of the multimedia content typically is encoded as a plurality of coded blocks using a discrete cosine transform (DCT) or other suitable transform, which, in general, transforms each block of content from the spatial domain to the frequency domain. In general, each coded block is represented by a plurality or matrix of coefficients, such as DCT coefficients.
Conventional watermarking methods, such as for use in watermarking digital images, include dividing watermark images into blocks and encoding the blocks using an appropriate transform. That is, the watermark image can be treated as an image and coded using a suitable image coding technique. The encoded watermark image then is added to or combined with an encoded version of content images to form a combined, encoded image. For example, coefficients representing the coded watermark image can be added to, inserted in or replace coefficients representing the coded content. Such conventional methods insert or replace watermark information in a fixed or predetermined manner, such as according to a given algorithm.
Although conventional watermarking methods of this kind attempt to reduce the amount of distortion introduced to the content as a result of the embedded watermark, there typically is at least some amount of distortion to the underlying content. Depending on the degree of the distortion to the content, the viewing experience of such content can be diminished. Alternatively, to reduce the existing amount of distortion to the content, some conventional watermarking methods eliminate or distort the watermark itself, e.g., by reducing the number of coefficients that represent the watermark image.